Oh, the irony -- as subsequent posts revealed, I got the math wrong too! Instead of 6 revolutions per second, it should actually be 10.
--- In Homebrew_PCBs@yahoogroups.com, "Andrew" <a_wake@...> wrote:
>
> I'd say the math is wrong on both sides. :)
>
> IIRC, his drum is around 6.5" diameter, to achieve 20.48 inches circumference. He is generating 20480 bits per revolution, giving the 1000 bits per inch.
>
> The drum is rotating 6 times per second, so 6 ∗ 20480 = 122880 bits per second. Somewhere in the earlier discussion, I think I saw that he is using 1 byte per bit (??? presumably to save the bit-shifting circuitry?), so that would work out to 122880 bytes/second. If he is using bit-shifting circuitry, so that each byte is 8 bits, then he can reduce that to 15360 bytes per second.
>
> Either way, it is a long way from 625000 bytes per second!!
>
> --- In Homebrew_PCBs@yahoogroups.com, "cunningfellow" <andrewm1973@> wrote:
> >
> > > Joh Elson wrote:
> > >
> > > Note that my photoplotter as it is cranks
> > > out a pixel every 5 us, so even as 8-bit
> > > bytes, that is 625,000 bytes a second.
> >
> > 16.384" drum
> > 1000 dpi
> > 600 RPM (10 r/s)
> > 1 bit per pixel
> > 8 bits per byte
> >
> > I get 20 kilobyte per second
> >
> > Am I missing something
> >
>